The present invention relates to the field of smart card technology. In particular, the invention provides a method and system for using a semiconductor chip in a plastic card with contacts for use with a smart card reader where the semiconductor chip is protected from electrostatic discharge (ESD).
A smart card is the size and shape of a credit card but has a miniature computer. The miniature computer enables the smart card to perform numerous functions that otherwise could not be performed by a card with a magnetic strip. For example, a smart card may contain user identification data that prohibits unauthorized use. Security is accomplished by using sophisticated cryptographic techniques for communication between the smart card and reading devices. For a general description, see, e.g., xe2x80x9cOverview and Applications of Smart Card Technology,xe2x80x9d at http://www.vitro.bloomington.in.us:8080/20g4/smrtcard.html; Jose L. Zoreda and Jose Manuel Oton, Smart Cards, (Artech House, Inc. 1994).
A smart card typically contains a Self-Programmable One-Chip Microcomputer (SPOM) with eight metallic metal pads, usually copper, for electronic contact points for communication of data between the smart card and a reading device. The contact points provide power, an input/output for serial data communication, a connection for reading the smart card clock signal, a connection for resetting the smart card, and a connection for the programming voltage of the smart card. Thus, only six of the eight contact points are generally used by present smart cards on the market; the other two are reserved for future use.
The size, function, and location of these contacts are dictated by an industry standard. ISO 7816-2 and 7816-3. This enables the various manufacturers and users of smart cards to create cards and compatible devices to work with the cards.
Smart cards generally contain Random Access Memory (RAM), Read Only Memory (ROM), and Electrically-Erasable Programmable Read Only Memory (EEPROM). The smart card processor typically has an 8-bit data path and 8-bit registers, and the card operates using an operating system selected for the particular application needs.
One aspect of smart cards is the method used for combining the appearance of the card and the need for contact points on the surface. Prior art includes printing verbiage and coloring the contacts with a process that may use either silk screen color or electroplated color. For example, a recently released Mastercard smart card consists of a chip module face with interlocking globes constructed of different contact materials, onto which were added a colored surface to produce letters and image outline.
Another feature of smart card technology is the need to protect the processor from electrostatic discharge (ESD). As the card is carried about, slid into and out of a card holder such as a wallet and slid into card readers, static charges accumulate on the card. When enough charge has accumulated at a particular point on the card, it will attempt to travel to the lowest potential voltage available to it. Typically this lowest potential is ground. If the accumulated charge travels to one of the contact points and through the processor in its attempt to reach a lower potential, the processor will be damaged. This happens because the charge that accumulates can be quite large compared to the maximum voltages and currents the processor is designed to accept. An ESD that travels through a processor is typically large enough to burn or otherwise damage transistors and conductors within the processor such that the processor becomes unoperational after receiving such a charge.
This invention presents a method and system for combining images, words, and identifiable patterns with the eight contact points of a smart card without using silk screen or electroplated color. In particular, the invention uses a single conductive surface, similar to a printed circuit board, from which a logotype is etched away, leaving the separated contact points. In particular, the contact points are shaped into a source identifier that an individual can immediately recognize and associate with a company, partnership or corporation.
Additionally, the present invention also provides a system that provides ESD protection for the processor by placing a grounded conductive path near the conductors to the semiconductor chip in such a manner so as not to disturb the appearance of the contact points whether they be shaped as a logo or otherwise.
The present invention accomplishes this by placing the conductive path on the back side of the substrate so that it is not visible. The contact points on the front side of the substrate are subject to the wear and tear of being slid into and out of wallets, card holders, purses, pockets, and card holders. Some contact points receive severe abrasions from this physical contact. Similarly, the protective conductor, when placed on the front side of the substrate, can be scratched and damaged as the card is used and carried about. It is possible that the ESD protective device could become scratched to the point where it can no longer conduct an ESD to the ground potential such that the ESD could travel through the semiconductor chip and damage it.
The present invention also allows implementation into an existing process without the need to alter the fabrication process involved in forming the contact points. Typically, contact points patterned into a logo are complicated in that multiple colors and layers are used to design them. Since the present invention is implemented in a non-visible portion of the smart card, or equivalent device, the addition of ESD protection using the present invention is less costly.
To achieve the stated and other objects of the present invention, as embodied and described below, the invention may comprise the steps of: etching a first conductive material on a back side of a substrate to form a plurality of bonding points coupled to a semiconductor chip and a conductive path directly coupled to one bonding point and being laid out in a proximal position to the remaining bond points; attaching said semiconductor chip to a back side of a substrate; creating holes through the substrate directly above the bonding points; and depositing and etching a second conductive material onto a front side of the substrate so as to form contact points which are electrically coupled to the bonding points via the holes through the substrate.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become more apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.